In typical imprinting techniques, such as a hot embossed or laser assisted nano-imprinting, an external high energy heating source is needed to heat imprinting material layers to melt the imprinting material layers. However, during the high temperature heating treatment of the imprinting material layer, a substrate is in a high temperature circumstance, so that circuit layout structures pre-formed in the substrate are damaged, and an ill effect of stress remaining on the surface of the substrate is caused by a large temperature difference.
In addition, an imprinting material adopted in an ultraviolet (UV) curing nano-imprinting technique is in a liquid state at room temperature. In the transferring of a pattern of a mold, the mold is pressed into the imprinting material, and then the imprinting material is cured by ultraviolet to transfer the pattern structure of the mold into the imprinting material. The mold adopted in the ultraviolet curing nano-imprinting technique has to be made of a material that is pervious to ultraviolet, such as a quartz mold, or a PDMS mold formed by a mold-making technique. However, the manufacturing processes of the quartz mold and the PDMS mold both are very complicated, and the quartz mold and the PDMS mold are difficult to be manufactured, so that the molds are expensive.
In a soft lithography nano-imprinting technique, special ink is adopted as a material for pattern definition. However, the special ink is very expensive, and the ink spreads when a feature pattern is defined to an imprinting material layer to cause a defect of the inaccurate definition of the feature pattern.
FIGS. 1A through 1F are schematic flow diagrams showing a conventional imprinting process. In a typical imprinting process, a substrate 100 is firstly provided, and an imprinting material layer 102 is coated on a surface 108 of the substrate 100, wherein the imprinting material layer 102 has to be made of a thermoplastic polymer material. Simultaneously, a mold 104 is provided, wherein a surface of the mold 104 is set with a pattern structure 106. As shown in FIG. 1A, in the step of providing the mold 104, the surface of the mold 104 with the pattern structure 106 is opposite to the surface 108 of the substrate 100 coating with the imprinting material layer 102.
Then, a heating step is performed to melt the imprinting material layer 102. The mold 104 is pressed into the melted imprinting material layer 102 to transfer the pattern structure 106 of the mold 104 into the imprinting material layer 102, such as shown in FIG. 1B. Subsequently, a heating source is removed. After the temperature is reduced to the value below the glass transition temperature of the imprinting material layer 102, a mold-releasing step is performed to separate the mold 104 and the imprinting material layer 102, so as to transfer the pattern of the pattern structure 106 of the mold 104 onto the imprinting material layer 102, such as shown in FIG. 1C.
Next, the imprinting material layer 102 is etched to remove a portion of the imprinting material layer 102 until a portion of the surface 108 of the substrate 100 is exposed, such as shown in FIG. 1D. When the exposed surface 108 of the substrate 100 is etched by using the imprinting material layer 102 remained on the surface 108 of the substrate 100 as an etching mask, a portion of the imprinting material layer 102 is easily removed to damage the transferring pattern. As a result, a distortion phenomenon occurs when the pattern is transferred onto the substrate 100. Therefore, a mask layer 110 is additionally formed on the imprinting material layer 102 and the exposed surface 108 of the substrate 100, such as shown in FIG. 1E.
After the formation of the mask layer 110 is completed, the imprinting material layer 102 and the mask layer 110 on the imprinting material layer 102 are removed by a lift-off process to expose the underlying surface 108 of the substrate 100. Then, the exposed surface 108 of the substrate 100 may be etched by using the remaining mask layer 110 as the etching mask to remove a portion of the substrate 100, so as to form a pattern structure 112 on the surface 108 of the substrate 100 to further transfer the pattern of the imprinting material layer 102 onto the surface 108 of the substrate 100. Subsequently, as shown in FIG. 1F, the remaining mask layer 110 and the imprinting material layer 102 are removed to complete the imprinting process.
In the conventional imprinting process, the imprinting material layer 102 has to be etched until a portion of the surface 108 of the substrate 100 is exposed, and then the mask layer 110 as the etching mask is set on the exposed surface 108 of the substrate 100. However, the step of setting the mask layer 110 is very complicated, and the procedures of firstly etching the imprinting material layer 102 and then setting the mask layer 110 increase the complexity of the process.